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151.
152.
153.
A preliminary optical classification of lakes in Estonia and south Finland which can also be used for small bays of the Baltic Sea is elaborated. The classification is based on the optical properties of water (diffuse attenuation coefficient, diffuse reflectance) and parameters that are routinely monitored in water bodies (Secchi depth, concentration of chlorophyll-a, total suspended matter and yellow substance). The data complex used for our classification covers different types of water ecosystems (ranging from oligotrophic to hypertrophic) and the variability of water constituent concentrations in the ice-free period in Estonia and south Finland. Using cluster analysis, we found 5 optical classes of waters: clear (C), moderate (M), turbid (T), very turbid (V) and brown (B). There is satisfactory correspondence between class of water, shape of diffuse attenuation coefficient and diffuse reflectance spectra and trophic state of the lakes. 相似文献
154.
The S/V Shoyo, of the Hydrographic Department, Japan Coast Guard, has conducted high-density expendable bathythermograph (XBT)
measurements along the 32.5°N line in the North Pacific every year from 1990 to 1993 as a part of the Japanese-World Ocean
Circulation Experiment (WOCE). These XBT data are analyzed here, focusing on year-to-year variations of the inventory and
core layer temperature (CLT) of the North Pacific subtropical mode water (NPSTMW). Large year-to-year changes are found in
the NPSTMW CLTs estimated in longitudes between 140°E and 160°E. CLT values were found of 17.4°C in 1990, 17.1°C in 1991,
17.3°C in 1992 and 17.6°C in 1993. Inspection of the wintertime westerlies over the formation area and sea surface temperature
distribution revealed that this change in CLT can be qualitatively attributed to the strength of atmospheric cooling in the
formation area in the previous winter. Although a large year-to-year variation of NPSTMW inventory was also found, it is hard
to state any relationship between CLT and atmospheric forcing. There is a possibility that different observational seasons
may affect the inventory. It has also been found that the thermocline depth in 1991 was shallower in the sea area east of
180° than in 1992 and 1993. Associated with this change, the North Pacific central mode water (NPCMW), characterized by thermostad
with temperatures ranging from 14°C to 11°C, appears in the sea area east of 180° in the 1992 and 1993 cross sections. The
1993 cross section, which ranged from the Japanese coast to the west coast of North America, possessed another thermostad
in the surface layer, with a temperature of about 17°C in the eastern part of the cross section, off California.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
155.
Following our previous study (Sugimoto and Hanawa, 2005b), we further investigate the reason why reemergence of winter sea
surface temperature anomalies does not occur in the North Pacific eastern subtropical mode water (NPESTMW) area, despite its
occurrence in the North Pacific subtropical mode water and North Pacific central mode water areas. We use vertical temperature
and salinity profiles of the World Ocean Circulation Experiment Hydrographic Program and Argo floats with high vertical and
temporal resolution, together with heat flux data through the sea surface. We point out first that one of the causes for non-occurrence
of reemergence is that the thickness of NPESTMW is very thin. In addition to this basic cause, two major reasons are found:
a vigorous mixing in the lower portion of NPESTMW and less heat input from the atmosphere in the warming season. Since, in
the lower portion of NPESTMW and deeper, the stratification is favorable for salt-finger type convection to occur compared
with the other mode water areas, vigorous mixing takes place. This is confirmed by both a large Turner Angle there and the
existence of staircase structures in vertical temperature and salinity profiles. From the viewpoint of heat input, the NPESTMW
area gradually gains heat in the warming season compared with other mode water areas. As a result, NPESTMW cannot be capped
so quickly by the shallow summer mixed layer, and water properties of NPESTMW are to be gradually modified, even in the upper
portion. 相似文献
156.
厦门嵩屿附近海底的冲淤变化 总被引:2,自引:0,他引:2
本文通过地形剖面测量比较、浅地层剖面勘探,结合水文泥沙测验和沉积物粒径资料,分析嵩屿附近海域在各历史时期和九江洪水期、枯水期的中淤变鼓水道近十几年来淤积速度加快。其主要原因是该海域动力要素明显减弱,携沙能力降低;其次,九龙江大量的泥沙主要集中在洪水期较短的时间内泄出河口,伴随涨潮流进入嵩鼓水道淤积。 相似文献
157.
An applied Fourier transform computation for the hydrodynamic wave-resistance coefficient is shown, oriented to potential flows with a free surface and infinity depth. The presence of a ship-like body is simulated by its equivalent pressure disturbance imposed on the un-perturbed free surface, where a linearized free surface condition is used. The wave-resistance coefficient is obtained from the wave-height downstream. Two examples with closed solutions are considered: a submerged dipole, as a test-case, and a parabolic pressure distribution of compact support. In the three dimensional case, a dispersion relation is included which is a key resource for an inexpensive computation of the wave pattern far downstream like fifteen ship-lengths. 相似文献
158.
桩式离岸堤保滩促淤工程消浪效果试验研究 总被引:9,自引:0,他引:9
在上海奉贤南北港保滩促淤工程中,采用了一种新型结构型式-桩式离岸堤,并通过物理模式试验进行了桩式离岸堤消浪效果研究。针对离岸堤通常建于近岸水区破波带的特点,重点研究水深,堤高以及堤身结构对波浪衰减的影响,同时对桩式离岸堤堤后水域的波浪底流速 分析探讨。研究结果表明,桩式离岸堤不仅具有良好的消浪效果。而且可在较大范围内改变波态,即由引起水体剧烈紊动的破波转变为浅水推进波,从而有效地改善海滩上的动力条件,促进海滩免受侵蚀,是一种具有广泛应用前景和新型保滩促淤结构。 相似文献
159.
杜勇 《中国海洋大学学报(自然科学版)》1989,(3)
作者采用非线性潮波方程,假定河口的宽度B(x)和深度h(x)是任意可微函数,导出了涌潮发生的条件,并讨论了各种变形情况下涌潮的形成。得出结论是,在涌潮形成过程中起决定作用的是浅水非线性效应,而河口变形效应则是起促进作用的。 相似文献
160.